(1) The Field of the Invention
This invention relates to processing apparatus. More precisely, this invention relates to rotary processors particularly useful for processing materials containing dispersed volatiles.
(2) Description of the Prior Art
Rotary processors are known to the art. Details relating to such processors are described in U.S. Pat. Nos. 4,142,805; 4,194,841; 4,207,004; 4,213,709; 4,227,816; 4,255,059, 4,289,319; 4,300,842; 4,329,065; 4,389,119; 4,413,913; 4,402,616; 4,411,532 and 4,421,412.
Essential elements of the basic individual processing passage of rotary processors disclosed in the above Patents comprise a rotatable element carrying at least one processing channel and a stationary element providing a coaxial closure surface operationally arranged to form with the channel an enclosed processing passage. The stationary element has an inlet for feeding material to the passage and an outlet for discharge of material from the passage. A member providing a material blocking and material collecting end wall surface is also associated with the stationary element and arranged near the outlet. The end wall surface is adapted to block movement of material fed to the passage and to coact with the moving channel walls to establish relative movement between the blocked material and the moving channel walls. This coaction permits material in contact with the moving walls to be dragged forward to the end wall surface for collection and/or controlled processing and/or discharge.
As disclosed in the above Patents, the processing passages present a highly versatile processing capability. The passages are adaptable for performing such processing operations as melting, mixing, pressurizing, pumping, devolatilizing and homogenizing, among others, as well as adding ingredients to or withdrawing ingredients from materials processed in the passage.
U.S. Pat. Nos. 4,329,065 and 4,413,913 relate to apparatus and method, respectively, for devolatilizing liquid materials. In accordance with the apparatus and method disclosed therein, material is fed to the processiong passage and, near the inlet, the material is spread as thin films on the sides of the rotating channel walls. A void space is provided downstream of the spreader and a vacuum source is connected to the void space so that volatile materials can be withdrawn from the surfaces of the thin films carried through the void space. The films may be respread on the channel walls at selected positions about the circumference of the passage to provide more than one void space where the renewed surfaces of the respread films can be exposed to vacuum. The thin films are carried forward through the passage toward the material collecting end wall surface where the films are scraped from the walls and collected for discharge. Usually the material is discharged to another devolatilizing passage where it is again spread on the walls and exposed to vacuum in the manner described to achieve the desired degree of devolatilization. A port opening in the stationary element provides communication between the vacuum source and the void space in the processing passage.
Commonly owned, copending U.S. patent application Ser. No. 532,166 filed on the same day as this application by P. S. Mehta, L. N. Valsamis and Z. Tadmor relates to novel apparatus and method for devolatilizing materials. Although Application Ser. No. 532,166 is not prior art, the apparatus and method disclosed therein is important to the background of this invention. Essentially the novel apparatus and method disclosed involve a devolatilizing stage which comprises a rotatable element carrying at least two annular channels and a stationary element providing a coaxial closure surface operationally arranged with the channels to provide at least first and last enclosed devolatilizing passages. The first devolatilizing passage of the stage includes an inlet associated with the stationary element for receiving material to be processed in the stage. The last devolatilizing passage of the stage has an outlet associated with the stationary element for discharging processed material from the stage. Each devolatilizing passage of the stage includes a blocking member associated with the stationary element which provides an end wall surface for the passage. The blocking members are arranged and adapted so that material fed to the passages of the devolatilizing stage can be carried forward by the rotatable channel walls to the end wall surfaces where movement of the carried forward material is blocked and the blocked material is collected for discharge from the passages. One or more transfer grooves are formed in the coaxial surface of the stationary element and positioned near the end wall surface(s). These transfer grooves are arranged to interconnect adjacent devolatilizing passages so that material blocked and collected in one passage can be transferred to an adjacent devolatilizing passage. Additionally, the devolatilizing stage includes a vacuum source arranged and adapted for operational communication with the devolatilizing passages.
The novel rotary processors of the invention of the above Application provide an improved devolatilizing stage which is designed to achieve devolatilization by way of a mechanism involving three steps: (1) nucleation of bubbles of volatiles material within the processing material, (2) growth of the bubbles and (3) rupture of the bubbles. This mechanism does not require spreading of the material on the channel walls as thin layers, but nevertheless provides extremely efficient mass transfer of volatiles from processing materials including viscous, viscoelastic materials. Copending application Ser. No. 532,166 is incorporated herein by reference.
The present invention provides a highly effective vacuum system for the devolatilization apparatus and methods disclosed and claimed in U.S. Pat. Nos. 4,329,065 and 4,413,913 and particularly for the novel devolatilization apparatus and methods of U.S. application Ser. No. 532,166.